default or selected kernelversion does not have config value CONFIG_BINFMT_EM86.
Result is shown for kernelversion 6.9.9

Kernel support for Linux/Intel ELF binaries

modulename: binfmt_em86.ko

configname: CONFIG_BINFMT_EM86

Linux Kernel Configuration
└─>Executable file formats
└─>Kernel support for Linux/Intel ELF binaries
In linux kernel since version 2.6.12  
Say Y here if you want to be able to execute Linux/Intel ELF
binaries just like native Alpha binaries on your Alpha machine. For
this to work, you need to have the emulator /usr/bin/em86 in place.

You can get the same functionality by saying N here and saying Y to
"Kernel support for MISC binaries".

You may answer M to compile the emulation support as a module and
later load the module when you want to use a Linux/Intel binary. The
module will be called binfmt_em86. If unsure, say Y.

source code:
depends
CONFIG_ALPHA